Recently I had a number of cases when I was contacted about the same assignment from different sources. One or even two agencies, a colleague with the same language combination and the actual client. How do I handle these requests in the most efficient way, which is for me that one when I get the assignment? Do I talk only to the client and ignore the rest? Do I offer the same price to everybody? Do I tell them or I do not that I was approached in multiple cases about the same job from other competitors? I do not yet know that best way to handle such cases. Therefore please advise from your own experience and practice. Thank you very much for your answers in advance!

In a local market where professional interpreters appear in the same lists (such as, for example, the aiic directory or directories of local associations), it happens again and again that several of us get the same inquiry from a direct client. It just happened to me a week ago, I provided intense consulting to the client on the phone on how to manage the interpretation at their event, put an offer together and sent it. At that point the date was still open, but a few days later they communicated the planned date and I called a colleague for an option to find out that she had also sent an offer and also talked to the client providing them advice. We agreed that this time it would have been awkward to inform the client that, no matter to whom they will award the job, they will be getting the two of us. I have often in the past in cases like these not submitted an offer and, instead, recommended the other colleague if I thought that the other colleague was the more suitable candidate (specialization). But in this case both of us had already offered a few days ago and are both candidates with relevant expertise.
The reason why I think we should actually not submit two offers for one and the same team is that I believe it artificially inflates the market (supply). If colleague A and colleague B both submit an offer for the same Job in a team of two to client x, client X believes that there are 4 super-qualified interpreters for them on the local market where in fact there are only A and B. Multiply this for languages like English, and clients in a given city believe that the supply of qualified interpreters is endless (i.e. a commodity, cheap). It is even worse for rarer languages. We should let our clients know that we are a rare species.
However, in the case described above it would have been a strange move to withdraw one of the offers made several days ago and explain that to the client. Should one of us get the job it will be the first time for me when a client will realize on site that they are still getting the interpreter whose offer they wordily declined a few months ago. Not ideal, I know.

Thank you, Julia for your substantial reply. It really concerns me that some clients go fishing for cheap interpreters while receiving valuable educational inputs (in form of free consulting as you rightly pointed out) from professional and more pricey colleagues for free. We invest our time, know-how and money for phone calls, and they end up booking the cheapest available option. In fact, it now only bothers be, in makes me truly angry.

Thank you for your comment. We are in the business of selling solutions to clients. Nowadays this is the case in many industries, actually many of my private market clients from all kinds of industries talk about standing out from the competition by selling solutions rather than products. Solutions always need explanation and consulting, and service, and they are bought based on the trust the potential client places in the person in front of him/her, the product does not matter at all. I do not regard these explanations as a service that I give away for free, they are an integral part of selling. You lose some deals and you make some - that is what selling is about.
We should all think of oursevels and the way we would buy a service. I would go for a cheap gardener, because it is only about cutting back some bushes and mowing the lawn. However, I would always go for the person I trust more rather than for the cheap offer if it is about decorating my bathroom or fitting my kitchen.

Dear msr, thank you very much for the links! They confirmed my intuitive decision to inform of the previously given option(s) but when I see that it's the client himself who comes as a third enquirer in that particular case I am no longer sure that I have to inform him or her that I gave quotes in two previous instances to intermediaries. Or should I do so? But again in that case do I not undermine my own quote? What do you think? Thank you.

...if it's the exact same job, prior options and their fate have no bearing on your availability for any of them, insofar as they're all for ...the same job, which can only (one hopes...!) be awarded once :-) - make sure they ARE for the exact same job, they could be for different parts thereof, albeit for the same time-lapse, ie different sub-meetings taking place in different halls at the same time, for some misguided reason being recruited for by different providers...

Furthermore, the existence of other potential recruiters vying for the same job should be known to that 3rd enquirer, ie the organiser, insofar as s/he's the one who asked them to submit their quotes - unless of course they're unsolicited quotes that potential providers are putting together - which, BTW, they should have told you.

In any case, for all of the reasons detailed in the previous posts the existence of other options - unless accepted under confidence - is no secret, whereas identities of optioners and terms should not normally be disclosed - only if authorised to do so.

In a nutshell, you may (as opposed to "must", which would apply for different jobs) disclose to the organiser the existence of prior options for the same job (but normally not their terms or authors), although the former info will probably be irrelevant for his/her purposes :-)... for this fact and inasmuch as it may be difficult to turn down a possible request - by the organizer! - for the info that you may not disclose, it may be safest IMHO not to mention prior options, in this case, particularly if you're averse to confrontational situations.